Selecting custom torque prescriptions for the straight-wire appliance.

Selecting custom torque prescriptions based on the treatment needs of each patient can reduce the amount of routine archwire torque adjustment needed and speed torque correction, thus reducing the total treatment time. Using the appropriate torque prescription prevents iatrogenic torque problems and allows most torque corrections to be done earlier with more resilient nickel-titanium and beta-titanium wires. As a result, fewer time-consuming final torque adjustments are needed with stainless steel finishing wires, resulting in shorter treatment time.

Predicting tooth-size discrepancy: A new formula utilizing revised landmarks and 3-dimensional laser scanning technology.

INTRODUCTION: The goal of this study was to develop a more accurate formula to forecast tooth-size discrepancies in patients based on not only the size of the whole teeth but also functional arch components derived from normal cusp-fossa interdigitation that should be obtained as the final treatment goal. METHODS: A total of 141 dental casts from Dr Larry Andrews' collection of "normal occlusions" that never received orthodontic treatment were scanned with an Ortho Insight 3D Laser Scanner (Motion View Software, Chattanooga, Tenn). Individual tooth sizes and portions of tooth sizes were measured with the Motion View Software. For each set of models, potential tooth-size discrepancies were calculated by using both the original Bolton analysis and the new Johnson/Bailey analysis developed by this team at the University of California at San Francisco (UCSF). Six tooth-size discrepancy ratios were computed and included the Bolton (2) and the new (4) Johnson/Bailey analysis ratios for the anterior arch component, posterior arch component, and overall ratio of the maxillary and mandibular arches. The Johnson/Bailey analysis utilized different landmarks and groups of teeth. It consequently divided the maxillary segment by the mandibular segment, in contrast to the Bolton ratios, which divided the mandibular sums by the maxillary totals. RESULTS: The Bolton anterior segment ratio ranged from 70.68 to 84.81, with a mean of 77.91 (SD, 2.43) (3.1%). The Bolton overall ratio ranged from 86.19 to 96.62, with a mean of 91.64 (SD, ±1.74) (1.8%). The Johnson/Bailey posterior discrepancy ratio ranged from 0.98 to 1.23, with a mean of 1.10 (SD, ±0.04) (3.6%). Its anterior discrepancy ratio ranged from 0.91 to 1.14, with a mean of 1.03 (SD, ±0.04) (3.9%). The Johnson/Bailey overall discrepancy ratio ranged from 0.98 to 1.15, with a mean of 1.06 (SD, ±0.03) (2.8%). CONCLUSIONS: Two methods were used to forecast tooth-size discrepancies between opposing arches in a sample with clinically acceptable occlusions. The new approach provided more specific ratios utilizing more clinically relevant functional arch components derived from dental cusp-fossa interdigitation.

Managing second molars.

Second molars can create great delays in orthodontic treatment if they are not managed intelligently. The purpose of this article was to describe common torque and position problems of the second molars and techniques for managing them. A simple technique for freeing mesially impacted second molars is presented.

Comparative analysis of traditional radiographs and cone-beam computed tomography volumetric images in the diagnosis and treatment planning of maxillary impacted canines.

INTRODUCTION: In this prospective study, we compared differences in the diagnosis and treatment planning of impacted maxillary canines between 2 imaging modalities. METHODS: Twenty-five consecutive impacted maxillary canines were identified from the pool of patients seeking orthodontic treatment. The first set of radiographs consisted of traditional 2-dimensional (2D) images including panoramic, occlusal, and 2 periapical radiographs. The second set comprised prints of 3-dimensional (3D) volumetric dentition images obtained from a cone-beam computed tomography (CBCT) scan. Seven faculty member completed a questionnaire for every impacted canine and diagnostic radiographic modality (2D and 3D). RESULTS: The data show that the judges produced different decisions regarding localization depending on the x-ray method. There were 21% disagreement (or discordance) in the perceived mesiodistal cusp tip position and 16% difference in the perceived labiopalatal position. In the perception of root resorption of adjacent teeth, there was 36% lack of congruence. Twenty-seven percent of the teeth that were planned to be left, recovered, or extracted with the 2D radiographs had different treatment plans when the judges viewed the 3D CBCT images (McNemar test, chi-square, 4.45; P = 0.035). The clinicians' confidence of the accuracy of diagnosis and treatment plan was statistically higher for CBCT images (P <0.001). CONCLUSIONS: These results showed that 2D and 3D images of impacted maxillary canines can produce different diagnoses and treatment plans.

Relative stiffness of beta titanium archwires.

The number of vendors of beta titanium (TMA type) wires has recently expanded dramatically. Samples of all the available sizes were obtained from most of the major beta titanium vendors. Three new square sizes are now also available. A total of 34 wire samples were tested for stiffness using the new ADA three-point wire-testing jig. Results show that not all beta titanium wires have the same stiffness. The range of variation was from small to large depending on the nominal wire size. There was also a spread of 1.67% to 4.27% in the standard deviation of the average stiffness from vendor to vendor. Burstone's Vari-modulus of elasticity is discussed along with how the properties of beta titanium could be integrated with his concepts. Strategies for using the new sizes of rectangular beta titanium wires for torque are discussed, including their use as working wires and finishing wires. The possibility of replacing stainless steel wires in the final finishing stages is also discussed.